1. Field of the Invention
The present invention relates to a developing device that uses developer to develop by means of an electrophotography development method, and more particularly to a developing device for preventing the scattering of developer outside the development area, and an image forming device equipped with same.
2. Background Information
Image forming devices such as printers, facsimiles, copying machines, etc. using an electrophotography development method are generally equipped with a photoreceptor and a developing device. An electrostatic latent image based on image data is formed on the surface of the photoreceptor, and a toner image is formed by developing this electrostatic latent image by means of a developing device that contains a developer.
Such conventional developing devices further provide a sealing member in order to prevent discharge of the toner outside of the development area. For instance, a magnetic sealing member formed from a magnetic substance has been used as the sealing member. This magnetic sealing member is provided with a fixed space in relation to the peripheral surface of the development sleeve at both ends of the longitudinal direction of the development roller. More specifically, for instance, as shown in Japanese Patent Application Publication No. 2003-15411, magnetic toner retained on the development sleeve by the magnetic force of a fixed magnet is restrained by the magnetic field formed in the gap between the end of the fixed magnet and the magnetic sealing member. This construction provides a seal which prevents magnetic toner from escaping by forming a magnetic brush composed particles of magnetic toner in the gap between the development sleeve and the magnetic sealing member.
However, one problem is that sufficient sealing capability will not be achieved with a construction which provides only the magnetic sealing member as described in the prior art. In other words, magnetic toner easily attaches to the peripheral surface of the development sleeve facing the internal end of the magnetic sealing member, because the magnetic force from the fixed magnet included in the development sleeve is concentrated generally within the internal end of the magnetic sealing member facing the peripheral surface of the development sleeve. Further, a member for controlling the thickness of the toner layer that extends towards the upper surface of the development sleeve (hereinafter, referred to as a “magnetic blade”) has generally been provided in the developing device at the upper side of the development sleeve. However, as the developing operation is repeated, the toner layer thickens on the peripheral surface of the development sleeve facing the internal end of the magnetic sealing member, and a force is applied that pushes the magnetic toner retained on the peripheral surface of the development sleeve outside the development area in order to increase the pressure of the toner with respect to the magnetic blade. Therefore, when this pushing force becomes greater than the magnetic confinement of the magnetic sealing member, the magnetic toner cannot be completely prevented from escaping. Accordingly, the magnetic toner easily leaks outside the development area by slipping through the magnetic sealing member. As a result, sufficient sealing capability is not achieved when providing only a magnetic sealing member, and an inability to control the discharge flow of magnetic toner outside the development area is realized.
An object of the present invention is to provide a developing device capable of achieving a stable sealing over a long period of time with a simple construction, and an image forming device equipped with same.